1. Field of the Invention
The present invention relates to a stepping drive unit for cameras which is capable of driving stepwise a photographic optical system by means of a member which is put into a reciprocating motion by electromagnetic force for the purpose of focusing.
2. Description of the Related Art
This type of stepping drive unit has been conventionally proposed in U.S. Pat. No. 4,560,266, and U.S. Pat. application Ser. Nos. 713,439, 713,473, 857,522, 857,524, and 835,966.
However, in such stepping drive units, the above-described photographic optical system is driven stepwise by repeatedly striking a ratchet for moving the photographic optical system with a claw member which is put into a reciprocating motion by electromagnetic force, and thus these units have suffered the disadvantage that the continuous sound of the impacts produced by the claw member hitting the ratchet can be heard externally to the discomfort of the user.